Lead is toxic to all tissues of the human body. The poisoning route can be inhaled through the respiratory tract, and then the phagocytes in the respiratory tract quickly carry it to the blood; or it can be absorbed through the digestive tract and enter the blood circulation to cause poisoning. The poisoned person generally has a history of contact with lead and lead compounds. A systemic disease mainly characterized by disorders of the nervous, digestive, and hematopoietic systems. Lead enters the blood circulation after being absorbed in an ionic state, and is initially distributed in various tissues throughout the body in the form of lead salts and combined with plasma proteins. After a few weeks, about 95% of the lead is deposited in the skeletal system and hair as insoluble lead phosphate. About 95% of the lead in the blood is distributed in red blood cells, mainly in the red blood cell membrane, and only 5% is in plasma. The lead phosphate deposited in the bone tissue is in a stable state and maintains a dynamic balance with the lead in the blood and soft tissues. The absorbed lead is mainly excreted through the kidneys, and can also be excreted through feces, milk, bile, menstruation, sweat glands, saliva, hair, nails, etc.